The objective was to determine relationships between protein and energy consumed from milk replacer and starter and first lactation performance of Holstein dairy cows. Data were collected from 4,535 Holstein animals from birth year of 2004 through 2014. Calves were received from 3 commercial dairy farms and assigned to 45 different calf research trials at the University of Minnesota Southern Research and Outreach Center from 3 to 195 d. Most calves were fed a 20% CP and a 20% fat milk replacer at a rate of 0.57 kg/calf per day. Milk replacer (MR) metabolizable energy (ME), starter ME, MR protein intake, and starter protein intake consumed from 0 to 8 weeks were (mean ± SD): 102.7 ± 13.2 Mcal/kg, 151.0 ± 42.2 Mcal/kg, 4.8 ± 1.0 kg, and 9.5 ± 2.7 kg, respectively. The MR ME, starter ME, MR protein intake, and starter protein intake consumed from first lactation production data was analyzed for 2,881 cows from the data set, which included 305-d milk, fat, and protein kg. Separate mixed model analyses were conducted with SAS to determine the effect of protein or energy consumed on first lactation production of milk, fat, and protein yield. Birth season, year, 6-week ADG class, and herd were included in the model with calf trial as a random effect. The 305-d milk and component production were positively affected by early life ME (P < 0.02) and protein intake (P < 0.03; Table 1). Greater ME and protein intake in the first 8 weeks of life resulted in increased first lactation milk and milk components yield. Table 1. Effect of combined protein and starter energy (Mcal/kg) and protein (kg) consumed 0-8 weeks (estimates are regression slopes) on first lactation 305-d milk, 305-d fat, and 305-d protein yield (kg; n=2,880)

Item	Variable	Estimate	SE	P-value
305-d milk	MR and Starter ME 0-8wk	4.03	1.55	0.009
	MR and Starter Protein 0-8wk	25.65	10.12	0.011
305-d fat	MR and Starter ME 0-8wk	0.17	0.06	0.005
	MR and Starter Protein 0-8wk	0.91	0.40	0.022
305-d protein	MR and Starter ME 0-8wk	0.14	0.04	0.001
	MR and Starter Protein 0-8wk	0.87	0.29	0.003